Demographic and ecological correlates of a recovering tiger (Panthera tigris) population: Lessons learnt from 13-years of monitoring
2020
Harihar, Abishek | Pandav, Bivash | Ghosh-Harihar, Mousumi | Goodrich, John
Efforts are on to recover tiger populations range-wide, but we lack suitable metrics to characterise and evaluate such recoveries. Identifying such metrics requires an understanding of tiger population dynamics and its ecological correlates in either recovering populations or those exposed to anthropogenic influences. We monitored a recovering tiger population from 2004 to 2017 in Rajaji National Park, India. Using photographic data and spatial capture-recapture models in an inviolate site vacated by pastoralists (zone 1), we identified demographic parameters of a recovering population. By contrasting it with a site that is presently occupied by pastoralists (zone 3) and one that is isolated (zone 3), we identified conditions facilitating recovery. In zone 1, connected to a large source population in Corbett Tiger Reserve, density increased from 2.08 tigers/100 km² to 7.07 tigers/100 km² corresponding to an annual growth rate of 4.5%. Density also increased in zone 2 (2.6 tigers/100 km² to 6.22 tigers/100 km²), but estimated apparent survival was 0.47 against 0.81 in zone 1. Recovery in zone 1 was accompanied by increased survival of females, while female tenure was shorter in zone 2. Due to the lack of functional connectivity, tigers in zone 3 are facing local extinction. Our results demonstrate that creating inviolate spaces to secure breeding populations and maintaining landscape-wide connectivity to expand breeding cores is critical for recovery. We highlight that relying solely on population increase may lead to unreliable inferences about population performance and instead suggest tracking survival and female land tenure to qualify recovery and success of conservation interventions.
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